Background & Objectives: Xanthan gum is produced by Xanthomonas bacteria. This gum is widely used in various industries. Random mutagenesis of xanthan-producing strains can increase xanthan production capacity several times. This study aimed to evaluate Xanthomonas mutant strains with high xanthan production capacity.Materials & Methods: The native strain of Xanthomonas citri K37 was affected by nitrogenic acid mutagen and after initial screening, the mutant strains were selected based on the appearance and diameter of the colony formed on the c dye medium. Whey-based production medium was used to produce xanthan gum and then production indices such as beta-galactosidase activity, sugar consumption, production rate, and viscosity of xanthan gum were selected in selected mutant strains.Results: A total of 8 mutant strains were selected among all treated colonies. Two high-yielding strains named R3 and R8 and two low-yielding strains called M2 and M6 were selected to evaluate the activity of beta-galactosidase enzyme and glucose consumption. Strain R3 increased viscosity and amount of xanthan compared to wild strain equivalent to 200 cp and 2 g / l, respectively, and mutant M6 lost the ability to produce xanthan.Conclusion: From the native Xanthomonas citri K37 isolate, a new R3 strain was created during mutagenesis, which can be effective in low cost cheese whey as a xanthan-producing strain.
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